This discussion of subordination owes a lot to Mightier Than the Sword
by C. E. Good.

First, what's a clause? According to Good, a clause is 'a bunch
of words containing a main verb'. There are two main kinds of clauses:

An independent clause is complete and
can stand alone.

examples:
Lions prefer to eatantelope.
orLions seldom eat zebra.

A subordinate or dependent clause is not complete and cannot stand
alone.

example: Although
lions eat zebra, ...

An independent clause may be introduced by a coordinating
conjunction (and, but, for, nor, or, so, yet) or may not need
introduction.

Subordinate clauses are more complex than independent clauses. There
are three kinds of subordinate clause (adverb clause, adjective
clause, and noun clause). Let's consider how each is introduced
and how each can cause problems.

The example above has two main
verbs: drank in the dependent clause and slept in the independent
clause. Although adverbial clauses seldom cause problems, sometimes you
may wish to reduce the adverbial clause to a phrase. After drinking
at the river, the lions slept.After drinking at the river
is not a clause because it lacks a main verb - it is a participial phrase
functioning as an adverb.

2. Using subordination, you can combine two
independent clauses into one sentence. 'The lions drank at the river.'
'The lions slept.' After they drank
at the river, the lions slept.Subordination has accomplished two things
here. First, it has connected two related ideas - thinking in general
and developing arguments in particular depend on these connections. Second,
subordination has allowed you to change sentence length and rhythm.

B. Noun Clauses (a second kind of subordinate
clause)

1. Poor writers have lots of problems with noun clauses. To understand
why, remember that nouns function as subject, direct object, object of
preposition, object of verbal phrase, appositive, and as subject complement
(I am skipping a few other functions).

Subject: Lions
do not live in jungles.

Direct Object: We
watched the lion.

Object of Preposition: We
quietly walked by the lion.

Object of Verbal Phrase (a participle in this
case): Watching
the lion, we remained hidden.

Appositive: The
antelope's main predator, the lion, does not live in jungles.
(an appositive is a word or phrase that restates the identity of a nearby
noun and is set off by commas. In this example, 'the lion' is an appositive.

Subject Complement: In
this food chain, the predator is the lion.

2. Like nouns, noun clauses function in all these ways. To demonstrate,
let's use the clumsy noun clause The fact that lions eat antelope in
the following sentences (modified from Good's book):

Subject: The
fact that lions eat antelope did
not impress Walt Disney.

Direct object: We
stated the fact that lions eat antelope.

Object of Preposition: Disney
was not concerned by the fact that lions eat antelope.

Object of Verbal Phrase: Stating
the fact that lions eat antelope, we waited for

Disney's response.

Appositive: We
stressed one thing, the fact that lions eat antelope.

Subject Complement: The
truth was the fact that lions eat antelope.

3. What should you do with noun clauses? First, learn to recognize them.
Noun clauses often start with the following:

that

why

the fact that*

where

what

whether

how

whoever

*the fact that is wordy and hackneyed. It can often be reduced
to that, leaving a more compact noun clause.

4. After recognizing noun clauses, determine whether they sound clumsy
and whether they are helping or hurting the independent clause. Finally,
reduce noun clauses to nouns or to phrases.

Example: The
fact that the lions live in groups partially
explains their hunting success.

Revision: The
social
behaviorof
lions partially explains their hunting success. We
replaced the noun clause with the adjective and noun socialbehavior.

Revision: By
living in groups,
lions increase their hunting success. We
replaced the noun clause with the participial phrase byliving
in groups.

1. Like adjectives, adjective clauses modify nouns. They are introduced
by relativepronouns:

that

whom

which

whose

who

example: The
lion, which rested by the river, seemed well fed.

example: The
lion that rested by the river seemed well fed.

A relative pronoun renames or refers to another noun and acts in its
place as the subject of the dependent, adjective clause. In the two examples
above, 'which' and 'that' rename 'the lion' and are the subjects of their
dependent clauses.

2. Adjective clauses starting with that
and which cause lots of trouble. Most trouble comes from excessive
usage, from stringing together these clauses. Replace adjective clauses
with adjectives, phrases, or adverbial clauses. These are more compact
and less distracting than relative clauses starting with that or
which.

example: We
studied the lions that were young.

revision: We
studied the young lions. (adjective
clause replaced by adjective)

example:
That leopards can swim across
rivers means that
they can cover much

territory
during rainy season.

revision: By
swimming across rivers,
leopards can cover much territory during the rainy season.

(adjective
clause replaced by participial phrase)

example: The
leopard, which was crossing the creek, could not detect the antelope.

revision: Because
the leopard was crossing the creek,
she could not detect the

antelope.
(adjective clause replaced by
adverbial clause)

'That away'. If the adjective clause is short
and has a subject other than that or which, you can often
delete the that or which.

example: The
antelope that the lion hunted was injured.

revision: The
antelope the lion hunted was injured.

example:The research project that
we proposed concerned predator-prey dynamics.